Biosca E G, Llorens H, Garay E, Amaro C
Departamento de Microbiología, Facultad de Biología, Universidad de Valencia, Spain.
Infect Immun. 1993 May;61(5):1611-8. doi: 10.1128/iai.61.5.1611-1618.1993.
Strains of Vibrio vulnificus biotype 2, isolated from internal organs of diseased European eels as pure cultures of opaque cells, together with some reference strains from Japanese eels, were used in this study. Spontaneous translucent-phase variants were obtained from the corresponding parent strains and compared for a variety of phenotypic traits related to virulence for eels. The rate of colony dissociation from opaque to translucent cells was higher (around 10(-2)) than that observed for translucent to opaque cells (10(-3) to 10(-4)). Electron microscopy with ruthenium red revealed the presence of a capsule of variable thickness on opaque cells, whereas translucent-type colonies had no observable capsular materials. No differences in plasmid profiles were detected between the two cell types so that plasmids do not seem to be implicated in the mechanism of phase shift of biotype 2 strains. No apparent difference in outer membrane protein and lipopolysaccharide patterns could be observed between the cell types. Both isogenic morphotypes were able to grow in eel serum and minimal medium supplemented with ethylenediamine di(O-hydroxyphenyl-acetic acid) or transferrin. Therefore, the presence of capsule was not required for the acquisition of iron from iron chelators or for resistance to serum bactericidal action. Both morphotypes were highly virulent for elvers, although the 50% lethal dose for translucent cells was higher than that for the corresponding opaque cells. The latter observation, together with the overall data, suggests that the production of capsular materials by biotype 2 of V. vulnificus is not essential for the development of vibriosis in eels, at least when cells are injected intraperitoneally.
从患病欧洲鳗鲡的内脏器官中分离出的创伤弧菌生物型2菌株，作为不透明细胞的纯培养物，与一些来自日本鳗鲡的参考菌株一起用于本研究。从相应的亲本菌株中获得自发的半透明相变体，并比较了与鳗鲡毒力相关的各种表型特征。从不透明细胞到半透明细胞的菌落解离率较高（约10^(-2)），高于从半透明细胞到不透明细胞的解离率（10^(-3)至10^(-4)）。用钌红进行的电子显微镜观察显示，不透明细胞上存在厚度可变的荚膜，而半透明型菌落没有可观察到的荚膜物质。在两种细胞类型之间未检测到质粒图谱的差异，因此质粒似乎与生物型2菌株的相转变机制无关。在细胞类型之间未观察到外膜蛋白和脂多糖模式的明显差异。两种同基因形态型都能够在鳗鲡血清和补充有乙二胺二（邻羟基苯基乙酸）或转铁蛋白的基本培养基中生长。因此，从铁螯合剂获取铁或抵抗血清杀菌作用不需要荚膜的存在。两种形态型对鳗鲡幼体都具有高毒力，尽管半透明细胞的50%致死剂量高于相应的不透明细胞。后一观察结果与总体数据一起表明，创伤弧菌生物型2产生荚膜物质对于鳗鲡弧菌病的发展不是必需的，至少在细胞腹腔注射时是这样。
